Power semiconductor device suitable for automation of production

ABSTRACT

The feature of the construction of this invention lies in a direct bond copper (DBC) pate. That is, a first Cu plate on which a semiconductor pellet is formed is fixed on the ceramic plate to continuously extend from the front surface of the ceramic plate to the rear surface thereof via one side surface thereof. Second Cu plates serving as electrodes of the semiconductor pellet are fixed on both sides of the Cu plate on the surface of the ceramic plate on which the semiconductor pellet is disposed. Electrode pads formed on the semiconductor pellet fixed on the first Cu plate are electrically connected to the second Cu plates by means of bonding wires. Since the the first Cu plate is continuously formed on the rear surface of the ceramic plate which is opposite to the surface on which the semiconductor pellet is mounted, the fixation surface of the semiconductor pellet is electrically connected to a heat sink plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a power semiconductor device having a largepellet size and used for motor control or the like.

2. Description of the Related Art

In a power semiconductor module, the technique utilizing the directbonding of copper to ceramic is disclosed in, for example, U.S. Pat. No.3,994,430 and IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. ED-23, NO. 8,AUGUST 1976, p 964, "A New Hybrid Power Technique Utilizing a DirectCopper to Ceramic Bond".

In the power semiconductor module utilizing the above technique, abuilt-in device is fixed on a plate called a direct bond copper (DBC)plate and constituted by directly attaching copper (Cu) to a ceramicplate. A heat sink is fixed on the rear surface of the DBC plate whichis the opposite surface of the fixing surface of the device. With thisconstruction, the number of manufacturing steps and the number of partsused can be reduced.

FIG. 1 is a perspective view of a conventional DBC plate fixed on a heatsink. A heat sink 1 may be formed of a Cu plate plated with nickel oraluminum plate, for example. A DBC plate 2 is fixed on the heat sink 1.The DBC plate 2 has a Cu plate 4 which is fixed on the surface of aceramic plate 3 and on which a semiconductor pellet (not shown) ismounted and Cu plates 5 used as electrodes of the semiconductor pelletand fixed on the surface of the ceramic plate. The ceramic plate 3 andthe Cu plates 4 and 5 are fixed together in a high-temperature oxidationatmosphere, for example. Although not shown in FIG. 1, a Cu plate isalso fixed on the rear surface of the ceramic plate 3.

The DBC plate 2 is fixed on the heat sink 1 by soldering, for example.The ceramic plate 4 which is insulative is disposed between the Cu plate4 and the heat sink 1. In a case where a product requiring that the Cuplate 4 on which the semiconductor pellet is disposed and the heat sink1 are electrically connected is manufactured, a terminal metal member 6is formed. The terminal metal member 6 is bonded at one end to the Cuplate 4 and bonded at the other end to the heat sink 1. With thisconnection, the Cu plate 4 on which the semiconductor pellet is disposedis electrically connected to the heat sink 1.

However, mounting of the terminal metal member 6 makes it difficult toattain automation of the mass-production line. First, it is difficult touse the mass-production line together with a mass-production line inwhich mounting of the terminal metal member 6 is not necessary.Secondly, enhancement of the mass-productivity is prevented by theadhesive quality and the precision of the mounting position of theterminal metal member 6.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a powersemiconductor device capable of reducing the number of parts used andthe number of manufacturing steps and attaining automation of anassembling line.

The above object can be attained by a power semiconductor devicesuitable for automation of production, comprising:

a ceramic-series insulative plate;

a first conductive plate fixed on the ceramic-series insulative plate tocontinuously extend from the front surface of the ceramic-seriesinsulative plate to the rear surface thereof via one side surfacethereof;

second conductive plates fixed on both sides of the first conductiveplate on the surface of the ceramic-series insulative plate;

a semiconductor pellet fixed on the first conductive plate;

wiring means for connecting electrode pads formed on the semiconductorpellet to the second conductive plates; and

a heat sink plate fixed on that portion of the first conductive platewhich is formed on the rear surface of the ceramic-series insulativeplate which is opposite to the surface on which the semiconductor pelletis disposed.

In this invention, since the conductive plate on which the semiconductorpellet is mounted is fixed on the ceramic-series insulative plate tocontinuously extend from the front surface of the ceramic-seriesinsulative plate to the rear surface thereof via one side surfacethereof, the number of manufacturing steps can be significantly reduced.Further, since the heat sink to be fixed in the later manufacturing stepis electrically connected to the semiconductor pellet without using anadditional part, mass-production can be easily and efficiently attained.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate a presently preferred embodimentof the invention, and together with the general description given aboveand the detailed description of the preferred embodiment given below,serve to explain the principles of the invention.

FIG. 1 is a perspective view showing the construction of a conventionalDBC plate;

FIGS. 2A and 2B are perspective views showing the construction of a DBCplate according to one embodiment of this invention;

FIG. 2C is a cross sectional view taken along the line 2C-2C' of FIG.2A;

FIG. 3 is a side view showing the construction of a power semiconductordevice manufactured by use of the DBC plate shown in FIGS. 2A to 2C; and

FIG. 4 is a top plan view of the power semiconductor device of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There will now be described an embodiment of this invention withreference to the accompanying drawings.

FIGS. 2A and 2B are perspective views showing the construction of a DBCplate according to one embodiment of this invention. FIG. 2A shows thesurface (front surface) of the plate on which a semiconductor pellet isdisposed and FIG. 2B shows the surface (rear surface) of the plate onwhich a heat sink is fixed. FIG. 2C is a cross sectional view takenalong the line 2C-2C' of FIG. 2A.

A Cu plate 11 on which a semiconductor pellet (not shown) is disposed isfixed on a ceramic plate 12 to continuously extend from the frontsurface of the plate 12 to the rear surface thereof via one side surfacethereof. Cu plates 13 serving as electrodes of a semiconductor pellet(not shown) are disposed on both sides of the Cu plate 11 on the surfaceof the ceramic plate 12 on which the semiconductor pellet is disposed.For example, the ceramic plate 12, Cu plates 11 and 13 are fixedtogether in a high-temperature oxidation atmosphere. Thus, a DBC plate14 is formed.

With the construction of the above embodiment, the Cu plate 11 is formedin a "letter-U" shape as shown in FIG. 2C, and the ceramic plate 12 isinserted into the groove defined by the "U"-shaped plate. Thus, the DBCplate 14 can be made simple in construction, can be easily fixed, andhas a high degree of heat conduction from the front to the rear surface.

FIG. 3 is a side view showing the construction of a power semiconductormodule manufactured by use of the DBC plate 14 of the aboveconstruction. In this case, FIG. 3 shows the construction from which anexternal casing and external leads are omitted. A semiconductor pellet15 is mounted on the Cu plate 11 by use of solder 16 or the like. The Cuplates 13 (electrodes) and electrode pads 17 on the semiconductor pellet15 are electrically connected together via bonding wires 18 formed ofaluminum.

The DBC plate 14 on which the semiconductor pellet 15 is mounted isfixed on a heat sink 19. In this case, since the Cu plate 11 is formedto continuously extend from the front surface of the insulative ceramicplate 12 to the rear surface thereof, the heat sink 19 and the DBC plate14 can be electrically connected to each other by normal bonding usingthe solder 16 or the like.

In a case where the semiconductor pellet 15 is a bipolar transistor, theheat sink 19 and the Cu plate 11 connected to the collector of thetransistor are electrically connected to each other. Therefore, theterminal metal member 6 becomes unnecessary.

According to the above embodiment, it is possible to provide anassembling line in which the number of assembling steps is reduced andwhich can be used together with a mass-production line in which mountingof the terminal metal member 6 is not necessary. As a result, themanufacturing cost can be reduced.

As described above, according to this invention, it is possible toprovide a power semiconductor device in which the number of parts usedcan be reduced, the number of manufacturing steps can be reduced andautomation of the assembling line can be easily attained by forming theCu plate on which the semiconductor pellet is mounted to continuouslyextend from the front surface to the rear surface of the DBC plate.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A power semiconductor device suitable forautomation of production, comprising:a ceramic-series insulative plate;a U-shaped first conductive plate defining a groove in which saidceramic-series insulative plate is inserted, said U-shaped firstconductivity plate continuously extending from the front surface of saidceramic-series insulative plate to the rear surface thereof via one sidesurface thereof; second conductive plates fixed on both sides of saidfirst conductive plate on the surface of said ceramic-series insulativeplate; a semiconductor pellet disposed on said U-shaped first conductiveplate; wiring means for connecting electrode pads formed on saidsemiconductor pellet to said second conductive plates; and a heat sinkplate fixed on that portion of said U-shaped first conductive platewhich is formed on the rear surface of said ceramic-series insulativeplate which is opposite to the surface of said U-shaped first conductiveplate on which said semiconductor pellet is disposed.
 2. A powersemiconductor device according to claim 1, wherein said first and secondconductive plates are conductive plates containing copper as a maincomponent.
 3. A power semiconductor device according to claim 1, whereinsaid first conductive plate is electrically connected to said heat sinkplate.
 4. A power semiconductor device according to claim 1, whereinsaid semiconductor pellet is a bipolar transistor having a base, anemitter and a collector, wherein the surface of said bipolar transistorfixed on said first conductive plate is said collector and said base andsaid emitter are connected to respective of said second conductiveplates.
 5. A power semiconductor device suitable for automation ofproduction, comprising;a ceramic plate; a first copper plate fixed onsaid ceramic plate to continuously extend from the front surface of saidceramic plate to the rear surface thereof via one side surface thereof,said first copper plate having a fixation surface in contact with thefront surface of said ceramic plate which is larger than a fixationsurface of said first copper plate in contact with the rear surface ofsaid ceramic plate; second copper plates fixed on both sides of saidfirst copper plate on the surface of said ceramic plate; a semiconductorpellet disposed on said first copper plate; a bonding wire forconnecting electrode pads formed on said semiconductor pellet to saidsecond copper plates; and a heat sink plate fixed on that portion ofsaid first copper plate which is formed on the rear surface of saidceramic plate which is opposite to the surface of the first copper plateon which said semiconductor pellet is disposed.
 6. A power semiconductordevice according to claim 5, wherein said first conductive plate iselectrically connected to said heat sink plate.
 7. A power semiconductordevice according to claim 5, wherein said semiconductor pellet is abipolar transistor and the surface thereof fixed on said firstconductive plate is a collector.
 8. A power semiconductor deviceaccording to claim 7, wherein said first conductive plate iselectrically connected to said heat sink plate.
 9. A power semiconductordevice according to claim 5, wherein said semiconductor pellet is abipolar transistor having a base, an emitter and a collector, whereinthe surface of said bipolar transistor fixed on said first conductiveplate is said collector and said base and said emitter are connected torespective of said second conductive plates.